The present invention relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides electrically operated well tools.
Actuators for downhole well tools are typically either hydraulically or electrically operated. Hydraulic actuators have certain disadvantages, for example, the need to run long control lines from the surface to the actuator, problems associated with maintaining a sealed hydraulic circuit, increased resistance to flow through the hydraulic circuit with increased depth, etc.
Electric actuators also have disadvantages. Some of these disadvantages are associated with the fact that typical electric actuators are either powered “on” or “off.” For example, in the case of solenoid-type electric actuators, the actuator is in one state or position when current is applied to the actuator, and the actuator is in another state or position when current is not applied to the actuator. This provides only a minimal degree of control over operation of the well tool.
Therefore, it may be seen that improvements are needed in the art of actuating well tools.